In our complex society today, numerous systems rely upon electrical power to function properly. Under normal circumstances, operating power is provided by the commercial AC power distribution system for heat, air conditioning, traffic lights, cooking, telecommunications, etc. Since many, if not all, major power distribution lines are located on poles or towers, a natural disaster, such as a tornado, hurricane, or blizzard, frequently causes the loss of commercial AC power. The failure of commercial AC power may constitute a significant danger to life or property depending upon the system impacted. For instance, failure of AC power supplying the lighting or air conditioning in a hospital or nursing home could readily result in loss of life. Therefore, backup power systems have been developed to assure that the loss of primary power does not seriously affect critical systems.
The one critical system most often taken for granted is the telecommunications system. Significantly, when an emergency occurs, virtually everyone expects that telephone communications will remain unaffected. Clearly, this is essential since it is through the telephone that we normally summon medical or rescue aid. Therefore, because of this essential nature, the telecommunications system has been provided with a complex backup power system in the event of commercial AC power failure.
Traditionally, backup electricity for telecommunications has been achieved by dispersing batteries throughout the telecommunications system to power the necessary switches, amplifiers, etc., of the system. These batteries, amounting to millions worldwide, are located in special rooms, in enclosures atop telephone poles, or even atop mountains, depending upon the local system needs. These batteries may be in place for years before a power failure requires them. Naturally, these batteries employ a very well understood and proven technology. However, the batteries require physical maintenance from time to time, and generally require a charging circuit to maintain them at a sufficiently charged state to perform their intended function. The power fraction, that is the power developed per unit of weight, is typically very low for lead-acid batteries because the components are inherently extremely heavy. Additionally, the lead is very toxic and, when the batteries are no longer useable, must be properly recycled. In flooded cell batteries, the acid electrolyte is also a significant hazard to those who must service the batteries, or to anyone who comes in contact with them. The very nature of charging lead-acid batteries from the commercial power system causes gassing and consumes some of the water that is a part of the electrolyte solution, thereby necessitating service. In the case of valve-regulated lead-acid (VRLA) batteries, including many types of "maintenance free" batteries, the electrolyte may not be serviceable and the batteries are permanently degraded. Additionally, because battery life and capacity are dependent on ambient temperature, the state of the electrolyte chemistry, and the condition of the grids, it is difficult and expensive to predict the battery reserve power available at any given time. However, experience has shown that telecommunication grade VRLA batteries in non-extreme environmental conditions exhibit a useful life of about four to five years, regardless of the manufacturer's claims.
One alternative to batteries as a backup power source might be a generator powered by a liquid fuel. Significantly, the power fraction for liquid fuels is many times higher than that of lead-acid batteries. Such power generators for both AC and SC power generation are quite common; most are gasoline engine driven. Gasoline however has several disadvantages for a backup power system that may not be needed for several years. Gasoline is actually a mixture of several chemical compounds, each with its own volatility. Over even a short period, the lighter (high volatility) compounds evaporate more quickly, leaving the heavier components behind. This fuel condition makes starting the engine more difficult; as the longer the fuel stands, or the warmer the ambient temperature is, more of the lighter compounds evaporate. Also over time, the more complex organic compounds may break down into simpler compounds that are not as readily useable as fuel. While many liquid fuels are highly volatile and evaporate readily, one liquid fuel that is significantly more stable than gasoline is methanol (CH.sub.3 OH). Among the organic compounds, methanol is one of the simplest compounds, and therefore does not break down into other components. Although methanol will readily evaporate if left open to the atmosphere, it will remain stable for an extended period of time if kept in a well-sealed container.
As with any system, liquid fuels have some drawbacks. In some respects, they are more difficult to handle and store than the typical battery, simply because they are liquid. Measuring the fuel remaining involves measuring a liquid volume. Because the fuel quantity is analog in nature, there are no readily established decision points for accomplishing a refueling. Also, some type of a pumping capability must be provided to move the fuel to the generator.
Accordingly, what is needed in the art is a backup power system that takes advantage of the high power fraction of liquid fuels, methanol in particular, while providing: (a) an ease of handling the fuel, (b) elimination of fuel evaporation, (c) long shelf life fuel storage, (d) controlled quality of the liquid fuel, and (e) an easy decision point for refueling.